The objective is to solve the structure and function of eukaryotic ribosomes, that encompasses a description of the location of each of the 80 proteins and of the 4 molecules of RNA, and then a definition of their individual and collective functions. Toward that end we propose to prepare individual rat liver ribosomal proteins in quantities sufficient to carry out sequence analyses. The intention is to determine the N-terminal sequence of as many proteins as possible; to determine the entire sequence of a selected few proteins; and to determine the sequence around the phosphorylation sites in proteins S6 and P1 and P2.